Electrochemical cells/batteries utilize an electrolyte solution as an ionically conductive medium. In an electrochemical cell using metal as the fuel, the metal fuel is oxidized during discharge to reducible metal fuel ions at a fuel electrode functioning as an anode. During charging, the reducible metal fuel ions are reduced to metal fuel at the fuel electrode, which is now functioning as a cathode, so the metal fuel thus plates the fuel electrode through electrodeposition.
In some electrochemical cells, the electrolyte solution may comprise an additive. Examples of such devices are shown, for example, in U.S. patent application Ser. No. 13/028,496, citing U.S. Pat. No. 6,027,827 and U.S. Pat. No. 7,722,988, all of which are incorporated herein in their entirety. Various additives for different electrochemical systems may include nitrate, lithium iodide, carbon dioxide, and sulfur dioxide. As seen in U.S. patent application Ser. No. 13/028,496, a useful additive for some electrochemical cells may comprise poly(ethylene glycol) tetrahydrofurfuryl (“PEG-THF”). During operation of some cells containing additives, the concentration of the additive in the electrolyte may fluctuate depending on the amount of additive co-deposited during charging the metal fuel or released therefrom during discharging. Among other things, the present application provides a cell configured to modulate the concentration of additives in the electrolyte solution.